The reigning UFC women's bantamweight champion wasted no time finishing off Sara McMann on Saturday night at UFC 170 in Las Vegas, landing the fastest knockout in UFC women's history with a brutal left knee to her opponent's liver only 1:06 into the opening round.

"We studied her videos and noticed no one really tried to hit her body," Rousey said. "She's a wrestler and has a bent posture so we thought it was the best thing to really concentrate on the liver shot for this camp."

In a fight between Olympic medallists - Rousey won judo bronze at the 2008 Olympics, while McMann won wrestling silver in 2004 - Rousey took control right from the opening bell and never looked back.

With McMann up against the cage, the 27-year-old Rousey began throwing elbows. Then, she went for the left knee and McMann crumbled to the floor.